Dipole or Yagi?

Discussion in 'On the Road' started by KE5RKE, Apr 30, 2021 at 1:18 AM.

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  1. KE5RKE

    KE5RKE Ham Member QRZ Page

    When I get my station all put together and get comfortable using the radio and communicating with folks, I'd like to start taking it on trips as a mobile in my truck. On the road, of course, I'll use a mag-mount antenna like most operators do. But when I get settled down in a campground, I thought I'd put up an antenna on my trailer to point at the nearest repeater. Figure to leave the radio in the truck and just change out the coax to hook up to the antenna on the trailer. I've had a few folks tell me to go with a Dipole or Yagi. I've been looking at DIY Dipoles and Yagis and they both look like fun projects. But why would I want to pick one over the other. I'm still reading my antenna books, but haven't gotten to a point that discusses the two in relationship to each other.

    I'm not trying to accomplish this now, just asking questions. (it's what I do best!) :rolleyes:
     
    YC8FMN likes this.
  2. KG7WGX

    KG7WGX XML Subscriber QRZ Page

    The simple answer is that a Yagi is a multiple element directional gain antenna, compared to a dipole. A dipole has a more omni-directional pattern, by comparison.

    However, there is no such thing as a free lunch. In order for there to be more power in a certain direction, there has to be less in others.

    You would use a map to determine the azimuth of the repeater you are trying to hit, then use a compass to roughly point the antenna in that direction. Clamp it so it won't turn into a windsock.

    (If you aren't familiar with Yagis, the shorter elements are directors and the longest element is the reflector. The driven element is somewhere in the middle. Aim the short end at the repeater. ;) )

    I've used an Arrow Yagi for accessing 2m repeaters when traveling and I got some pretty good results with only 5 watts. The thing I really liked was that it knocked down into a small bag when not in use, which maked it really easy to pack without worrying about bending something.
     
    KE5RKE and N8ZL like this.
  3. KE5RKE

    KE5RKE Ham Member QRZ Page

    Thanks, much appreciated.
     
  4. W7HV

    W7HV Ham Member QRZ Page

    HF or using V/UHF repeaters? If the later, you'll want vertical polarization which means the yagi will be vertically oriented, and being pretty directional, well need to be rotated to point in the desired direction(s). HF is another thing entirely.
     
  5. KD4UPL

    KD4UPL Ham Member QRZ Page

    First, for actual mobile VHF/UHF operating, don't let all the people using mag mounts lead you to believe it's a good idea. A actual attached antenna will generally out perform a mag mount. It won't scratch your paint all up and it won't make you crush the coax in the door or window as it enters the vehicle. A bolted fender mount, thru hole roof mount, or even a set screw lip mount would be a better choice then a mag mount. In my opinion mag mount antennas are for temporary installations, lazy people who don't want to do a proper install, and those who have an irrational fear of lowering the resale value of their vehicle.
    If you have a good mobile antenna it's quite possible that you will gain nothing by putting a different antenna on the RV; it just depends on how far away the repeaters are you are trying to access. For FM work you want vertical polarization which is more difficult with a dipole than a yagi. If your mobile whip is a 5/8 wave it may already have some gain over a dipole anyway.
    A yagi, vertically polarized, would be the best choice for trying to really boost your range over a mobile whip.
     
  6. KE5RKE

    KE5RKE Ham Member QRZ Page

    Thanks for that. I apologize for not responding sooner.........I've been out of town for the past 4 days.

    All good info. Thanks.

    This is the antenna I'm considering building. I liked it because it could be oriented either horizontally or vertically. And it just looked like a fun build project.

     

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